Certain types of valve arrangements (e.g., valve manifolds, cartridge valves, etc.) use a self-regulating hydraulic circuit design for the control of flow rate by a current-controlled signal. This circuit design (also known as a Valvistor® design) achieves servo-type control of a main poppet without using an electrical feedback transducer. In particular, the main poppet amplifies a small flow through a pilot circuit, comparable to a transistor. Such valve arrangements may be used in a wide range of applications with hydraulic cylinders and motors. Non-limiting examples of such applications include casting, deep drawn presses, injection molding, container handling, shovel loaders, forestry, and dump trucks.
FIGS. 1-3 show the construction of conventional valve arrangements using self-regulating hydraulic circuit designs. FIG. 1 is a cross-sectional view of a valve arrangement 100 including a system chamber 102 and a pilot chamber 104. The system chamber 102 includes a manifold 110 and a poppet 120. The pilot chamber 104 includes a pilot valve 130. In general, the system chamber 102 defines a main flow circuit and the pilot chamber 104 at least partially defines a pilot flow circuit.
The manifold 110 defines a first opening 111 that leads to an internal bore 113. The manifold 110 also defines a second opening 114 that leads to the internal bore 113 to form a main flow path. In the example shown, the first opening 111 defines a first port P1 and the second opening 114 defines a second port P2. Each port P1, P2 may function as an inlet and/or an outlet for fluid flow. The inlet receives fluid having system pressure and the outlet leads to the reservoir tank. In the example shown, the second opening 114 is oriented generally orthogonal to the first opening 111 and the first passage 116.
The manifold 110 also defines a variable volume region 117 at an opposite end of the bore 113 from the first opening 111. A passage 116 leads from the variable volume region 117 to the pilot chamber 104. The pilot valve 130 selectively directs fluid received from the passage 116 to a second passage 118 that leads to the second port P2 of the manifold 110 as will be described in more detail herein. The variable volume region 117, passage 116, and second passage 118 form a second flow path.
The poppet 120 is configured to slide within the bore 113 of the manifold 110 along first and second directions A1 and A2. The poppet 120 generally divides the manifold 110 into a first section defining the main fluid circuit and a second section defining the second fluid circuit. The volume of the region 117 varies as the poppet 120 slides within the bore 113 in the first and second directions A1, A2. Movement of the poppet 120 in the first direction A1 opens the main fluid circuit between the first and second ports P1, P2 and reduces the volume of the region 117. Movement of the poppet 120 in the second direction A2 closes the main fluid circuit and enlarges the volume of the region 117.
In certain implementations, the manifold 110 includes an angled seat 112 against which an angled contact surface 123 of the poppet 120 may be pressed to close the main fluid circuit. Engagement between the contact surface 123 and the angled seat 112 forms a seal between the first and second ports P1, P2. When the poppet 120 opens the main fluid circuit, fluid flows from the first port P1, past the angled seat 112, to the second port P2. Movement of the poppet 120 in the first direction A1 moves the contact surface 123 of the poppet 120 away from the seat 112 of the manifold 110 and movement of the poppet 120 in the second direction A2 moves the contact surface 123 towards from the seat 112.
As shown in FIGS. 1 and 2, the poppet 120 includes a body 121 having a top 125 and a bottom 126. In the example shown, the body 121 also has one or more annular side surfaces that extend between the top 125 and bottom 126 of the poppet 120. In other implementations, the sides of the poppet 120 may define any desires shape. The body 121 defines a through-channel 122 extending from the bottom 126 of the poppet body 121 to an orifice 124 defined in the annular side surface of the poppet body 121 towards the top 125 of the body 121. In the example shown, the orifice 124 is an elongated slit. In other implementations, the orifice 124 may be any desired shape.
When the poppet 120 is disposed in the manifold 110, the bottom 126 of the body 121 faces the first opening 111 of the manifold 110 and the top 125 of the body 121 faces the variable volume region 117. The poppet body 121 and the manifold bore 113 are sized and shaped so that the orifice 124 of the poppet 120 is at least mostly covered by an inner surface of the bore 113 when the poppet 120 is in a seated position (i.e., when the poppet contact surface 123 engages the manifold seat 112). The poppet body 121 and manifold bore 113 are further sized and shaped so that the orifice 124 is increasingly exposed to the variable volume region 117 as the poppet 120 moves away from the manifold seat 112 in the first direction A1.
The pilot valve 130 includes a proportional two-position valve having an inlet 132 and an outlet 134. The inlet 132 is in fluid communication with the variable volume region 117. The outlet 134 is in fluid communication with the manifold passage 118. Movement of the pilot valve 130 is electrically controlled (e.g., by a proportional solenoid). When the pilot valve 130 is in the first position, the inlet 132 is isolated from the outlet 134. As the pilot valve 130 moves towards the second position, the second fluid path is increasingly opened between the inlet 132 and the outlet 134.
Fluid entering the manifold 110 through the first port P1 pushes against the bottom 126 of the poppet 120 in the first direction A1. Fluid located in the variable volume region 117 applies pressure to the top 125 of the poppet 120 in the second direction A2. The poppet 120 is held in a stationary position within the bore 113 when the pressure within the region 117 is in equilibrium to the pressure of the fluid at the first port P1. When the pilot valve 130 is closed, the fluid in the region 117 remains in the region and the poppet 120 is maintained in position. In certain implementations, a sufficient amount of the metering orifice 124 is exposed to enable some fluid to pass through the passage 122 from the inlet 111, through the metering orifice 124, to the region 117 to maintain equilibrium.
When the pilot valve 130 opens, fluid flows from the variable volume region 117 through the passage 116, through the open pilot valve 130, and to the second passage 118. The reduction is fluid reduces the pressure within the region 117 until the system pressure (i.e., the pressure of the fluid at the inlet 111) is sufficient to move the poppet 120 in the first direction A1. As the poppet rises, fluid flows from the first port P1 to the second port P2. In addition, fluid flows from the first port P1, through the passage 122, through the metering orifice 124, and into the region 117. When the poppet 120 rises enough to allow sufficient fluid to enter the region 117 to offset the loss to the tank, the pressure within the region 117 will begin increasing until equilibrium is restored, thereby holding the poppet in a stable raised position.
As shown in FIG. 3, the inlet and outlet of the valve arrangement 100 may be reversed by substituting the poppet 120 for another poppet 120′ and by routing the fluid path 118 past the second opening 114 to the first opening 111. The second example poppet 120′ shown in FIG. 3 defines a passage 122′ having a first end that aligns with the second opening 114 and a second end that defines a variable orifice 124 towards the top of the poppet 120′. The passage 122′ is sized and structured so that fluid from the second opening 114 flows to the variable volume region 117 until equilibrium is reached between the system pressure and the pilot pressure in substantially the same way as described above.
Improvements to valve arrangements having self-regulating hydraulic circuit designs are desired.